Polyester is a heat-resisting, highly elastic strength synthetic resin with excellent chemical resistance, and is used for reinforced plastics. For example, polyester is widely used for car bodies, bodies of motor boat, and furniture, and also as a fiber material for clothes.
From among polyesters, biodegradable polyester-based polymers are polymers that may decompose to water and carbon dioxide, or water and methane gas by microorganisms existing in the nature such as bacteria, algae, and fungi. Such biodegradable polyester-based polymers do not cause environmental pollution and thus are environment-friendly.
Biodegradable polyester-based polymers can be produced by a condensation reaction of, for example, diol and diacid. There are various kinds of polyester-based polymers including aliphatic polyester-based copolymers and aromatic polyester-based copolymers as examples of the biodegradable polyester-based polymers.
Biodegradable polyester-based polymers can be produced through an esterification reaction and a polycondensation reaction. In the esterification reaction, oligomers are produced by a condensation reaction, and in the condensation reaction, a polymer is produced from the oligomers.
In producing biodegradable polyester-based polymers, to shorten a reaction time, various branching agents are used in a method of preparing a biodegradable polyester-based polymer. Particularly, isocyanates and other multifunctional acids or alcohols are used as branching agents.
Conventional aliphatic branching agents for preparing a biodegradable polyester-based polymer have a problem in that a yellowness index of polymers obtained by polymerization is high. In addition, conventional methods for preparing a biodegradable polyester-based polymer have a problem in that the polymerization time is long because branching agents have low reactivity and are not homogeneously dispersed in a reaction mixture.